@model IEnumerable<string>
<a class="btn btn-block btn-secondary" asp-action="List" asp-controller="Product" asp-route-category="">
  Home
</a>
@foreach(string category in Model){
  <a class="btn btn-block @(category==ViewBag.SelectedCategory?"btn-primary":"btn-secondary")" asp-action="List" asp-controller="Product" asp-route-category="@category" asp-route-productPage="1">
    @category
  </a>
}
